In the US, the expected statistical figures for breast cancer in 2013 are estimated at approximately 230,000 new cases and 40,000 deaths. The mortality rate can be lowered if breast cancer could be detected in an earlier stage. Screening with X-ray mammography has been the gold standard for early detection of breast cancer. However, it is believed that in about 40% of the screening population typically more than 50% of their breasts are made up of dense fibro-glandular breast tissues that tend to obscure abnormalities in X-ray mammograms. Recent clinical studies report that this “dense breast” gap could be economically and sufficiently dealt with using breast ultrasound. Currently, an automated-scan breast ultrasound system that received USFDA approval for breast cancer screening uses a chestward compression automated scanning procedure with an ultrasound transducer contacting the breast through a membrane. Such system is available from GE Healthcare under the name Invenia ABUS, and a similar system is believed available at least in Europe from Siemens Healthcare. A breast ultrasound system using scanning that is partly automated and partly manual, where the transducer contacts the breast through a camisole and a nipple pad, is reported by SonoCine, Inc. of Reno, Nev. A system in which the transducers are acoustically coupled with the breast through a liquid and produces CT-like slice images of the breast, is reported by Delphinus Medical Technologies, Inc. of Plymouth Mich.
There are two major challenges facing practical breast cancer screening modalities. The first is cost, which can be measured as the cost of the actual examination and assessment of the results, and as the cost per detected cancer. Since breast cancer has low prevalence rate such that one cancer is generally found in 200 to 300 asymptomatic patients screened, the per patient screening cost must be kept low, currently typically to the range of $100-$200 in the U.S., in order to achieve a reasonable cost per cancer detected (i.e. $20,000 to $60,000 range). This cost range generally translates to limiting typical reading/interpretation time to about 3 minutes per patient, using an automated scanning system with a throughput of over 2,000 patients per year. For standard screening x-ray mammography, where only 4 new images are generated per patient at a screening examination in typical U.S. practice, this 3-minute interpretation time goal is relatively easily met. However, for current commercial breast ultrasound screening examinations, where hundreds or even thousands of new two-dimensional (“2D”) thin-slice images per patient are obtained under chestward compression, in planes transverse to the coronal plane (often called “original” images), the goal of 3 minutes of reading/interpretation time is difficult to meet. An associated reading method can be used by configuring the original thin-slice images first into coronal thin-slice images and then into composite coronal thick-slice images, e.g., 2-30 coronal thin-slice images into one thick-slice image, so that a user can better search for abnormalities and better manage the reading/interpretation time. See for example U.S. Pat. No. 7,828,733, where the coronal thick-slices method is discussed. However, this method is still not quite fast enough, nor does it satisfactorily solve the “oversight” challenge described immediately below.
The second major challenge of breast cancer screening is “oversight,” i.e., overlooking obvious cancers. A delay in cancer detection due to oversight can cause the cancer to progress to a more advanced stage resulting in decreased patient survivability and increased treatment cost. This problem is particularly serious when health professionals attempt to read/interpret breast images quickly. A study on blind re-reading of 427 prior screening x-ray mammograms, which were taken a year before the cancer detection, published in Radiology (by Warren-Burhenne, et al., 2000, Vol. 215, pages 554-562), reports that as many as 115 (or 27%) of the cancers could have been detected a year earlier and should be classed as oversights. In order to reduce the oversight problem, commercial computer-aided diagnosis (“CAD”) systems have been developed for X-ray mammography screening. Development of clinically useful x-ray mammography CAD was no trivial matter, as the CAD must achieve sensitivity close to that of human readers. The development was undertaken by several commercial firms, some in collaboration with universities and national laboratories, over many years, and is believed to have consumed over $100 million in combined developmental cost. The CAD's impact in x-ray mammography is clearly visible—after 10 years of its commercial introduction, as reported by a study published in JACR (by Rao et al., 2010, Vol. 7, pages 802-805), by year 2008 75% of the screening x-ray mammograms were read with CAD assistance.
In the known commercial automated 3D breast ultrasound systems, the ultrasound beam is generally directed chestwardly during the scan while the breast is generally compressed chestwardly down. This method has significant advantages over the earlier non-chestward-compressed ultrasound scanning method proposals, such as a method that clamps the breast between vise-like scanning plates, as in standard x-ray mammography. The advantages of chestward scanning include: improved patient comfort, lesser depth of breast tissue that needs to be imaged during the scan, and the possibility of employing higher ultrasound frequency resulting in greater image quality. This is discussed in more detail in U.S. Pat. No. 7,828,733. A composite coronal thick-slice method (2-20 mm in slice thickness), which could be used as a guide or road map to aid the search for abnormalities, is also discussed in U.S. Pat. No. 7,828,733, as is the possibility of a full-breast composite image 2502 that preferably is a CAD enhanced expression of the sonographic properties of substantially all of the tissue imaged by the volumetric ultrasound scans, and of enhancing lesions according to their likelihood of malignancy (or another metric of interest). The thick-slice coronal image has proven helpful as a road map in current commercial automated 3D breast ultrasound systems. In commercial systems, a popular slice thickness of the coronal thick-slice image is believed to be 2 mm, which is selected for reasons of good image quality and less chance to miss smaller lesions or abnormalities. Slice thicknesses down to 0.5 mm also are believed to be used.
In known commercial automated 3D breast ultrasound screening systems using chestward compression scans, for each patient, several scans are typically made on each breast, for example 2-5 scans, although in some cases it can be a single scan and in some cases more than 5 scans. Each typical scan generates about 300 new images. Thus, 1,200 to 2,400 or more new images can be generated for each patient. With the manifold, e.g., 300- to 600-fold increase in the number of new images over screening x-ray mammography, readers can encounter even more oversights than the 27% or so that can be encountered in screening x-ray mammography. Thus, there is a need for efficient methods and systems to better manage both the reading/interpretation time as well as the oversight problem before breast ultrasound screening can be even more broadly employed to help more women.
Since the worldwide introduction of automated 3D breast ultrasound using chestward compression several years ago, radiologists at hundreds of facilities around the world have been struggling to read/interpret the huge volume of breast ultrasound images per patient study. At the present time, it is believed that only the best readers, even using the known composite 2 mm coronal thick-slice images as road maps, are able reach the 3 minutes practical goal per patient, while the majority of the readers are averaging more than 5 to 8 minutes per patient. No published studies are known on the “oversight” in current commercial automated 3D breast ultrasound, but one could guess that the oversight rate would not be below that found for screening mammography, i.e., the reported 27%.
The subject matter claimed herein or in a patent issuing from this patent specification is not limited to embodiments that solve any particular disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.
All the publications, including patents, cited throughout this patent specification, are hereby incorporated by reference.